Side dams forming a liquid steel pool, with a pair of cooling drums interposed therebetween, in twin-drum continuous strip casters are required to have high corrosion resistance against stainless and other steels, high wear resistance to friction with the drums, high resistance to the thermal shock occurring when hot metal is poured and a low enough thermal conductivity to inhibit the adhesion of skulls.
Conventionally Al2O3+C, Si3N4, BN, Sialon, AlN, TiB2, TiN, Si3N4+BN, Si3N4+AlN+BN, Sialon+BN, Sialon+AlN+BN, Sialon+TiB2+BN, Sialon+TiN+BN and some other types of ceramics have been used for side dams. However, none of them have proved to have the long life required of side dams.
Generally Al2O3+C ceramics, which have high corrosion resistance to molten steel and good thermal shock resistance, tend to become roughened where contact is made with moving drums and, thus, show poor sealability to molten steel. While having high resistance to penetration of molten steel, Si3N4, Sialon, AlN, TiB2, and TiN ceramics do not have good corrosion resistance. Because of poor thermal shock resistance, they tend to crack when subjected alone to rapid heating and cooling.
While having good thermal shock resistance, BN ceramics are soft and do not have good wear resistance. Because of high thermal conductivity, they tend to cause the adhesion of skulls to plates, thereby inhibiting the implementation of stable continuous casting.
Combinations of BN ceramics with Si3N4, Sialon, AlN, TiB2, and TiN ceramics sometimes exhibit better thermal shock and wear resistance than those seen when they are used alone. However, the problem of poor corrosion resistance remains unsolved.
As described above, conventional ceramics do not have the good reliability required of structural materials because they do not have the desired high corrosion, wear and thermal shock resistances and do not have low thermal conductivity.